Your "biological clock" may be mostly in your head–and an actual clock can trigger it researchers from Florida State University have discovered. Through two experiments, they sought to test whether a literal ticking clock would prime women to think about their reproductive timing differently.

The first experiment had participants, both male and female, fill out a survey about the ages at which they'd like to get married and have children. The second asked participants to weigh qualities like attractiveness, kindness, and social status when considering a mate. Both experiments also asked participants to recall their socioeconomic status during their childhood, by having them agree or disagree with statements like "My family usually had enough money for things when I was growing up." Some participants filled out their answers while seeing and hearing a ticking timer nearby.

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The results, published in the journal Human Nature, show that a reminder as subtle as a ticking clock can trigger some women to want to start a family at an earlier age. Female participants who had low socioeconomic status as children said they wanted to get married and have kids at an earlier age, but only when in the presence of the clock. In the second experiment, they also de-emphasized the importance of social status in a partner, which is often important for long-term planning, and instead put more weight on attractiveness when the clock was nearby.

But a ticking clock didn't produce the same results for women who had high socioeconomic status as kids. In the first experiment, it didn't change their answers about age. And in the second experiment, their results were the exact opposite–when faced with a stress, researchers say, higher status women tend to delay parenting and focus on longer-term goals. Men in either group showed no change from the ticking clock, showing that the "biological clock" is mainly a female issue.

Why the economic difference? Researchers say women with low resources at a young age are taught that their long-term prospects may be poor, so they tend to focus on the short term when faced with a threat–even a subtle, implicit one like a clock ticking. "The findings suggest that a woman's childhood years can interact with subtle environmental stimuli to affect her reproductive timing during adulthood," researcher Jon Maner said in a statement.